**EXHIBIT 31.1**

**CERTIFICATIONS**

I, Sherri C.Oberg, certify that:

1.             Ihave reviewed this quarterly report on Form 10-Q of Acusphere, Inc.;

2.             Basedon my knowledge, this report does not contain any untrue statement of amaterial fact or omit to state a material fact necessary to make the statementsmade, in light of the circumstances under which such statements were made, notmisleading with respect to the period covered by this report;

3.             Basedon my knowledge, the financial statements, and other financial informationincluded in this report, fairly present in all material respects the financialcondition, results of operations and cash flows of the registrant as of, andfor, the periods presented in this report;

4.             Theregistrant’s other certifying officers and I are responsible for establishingand maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e)) for the registrant and we have:

a)             Designed such disclosure controls and procedures, orcaused such disclosure controls and procedures to be designed under oursupervision, to ensure that material information relating to the registrant,including its consolidated subsidiaries, is made known to us by others withinthose entities, particularly during the period in which this report is beingprepared;

b)             [Paragraph omitted in accordance with SEC transitioninstructions contained in SEC Release Nos. 34-47986 and 34-49313];

c)             Evaluated the effectiveness of the registrant’sdisclosure controls and procedures and presented in this report our conclusionsabout the effectiveness of the disclosure controls and procedures, as of theend of the period covered by this report based on such evaluation; and

d)             Disclosed in this report any change in the registrant’sinternal control over financial reporting that occurred during the registrant’smost recent fiscal quarter (the registrant’s fourth fiscal quarter in the caseof an annual report) that has materially affected, or is reasonably likely tomaterially affect, the registrant’s internal control over financial reporting;and

5.             Theregistrant’s other certifying officers and I have disclosed, based on our mostrecent evaluation of internal control over financial reporting, to theregistrant’s auditors and the audit committee of the registrant’s board ofdirectors (or persons performing the equivalent functions):

a)             All significant deficiencies and material weaknesses inthe design or operation of internal control over financial reporting which arereasonably likely to adversely affect the registrant’s ability to record,process, summarize and report financial information; and

b)             Any fraud, whether or not material,that involves management or other employees who have a significant role in theregistrant’s internal control over financial reporting.

 
| Date: May 12, 2006 |   |                          |
|-------------------------|--------|-------------------------------|
|                    |   |                          |
|                    |   | /s/ SHERRI C. OBERG           |
|                    |   | Sherri C. Oberg               |
|                    |   | Chief Executive Officer       |
|                    |   | (Principal Executive Officer) |

 

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